Adjustable railings on conveyor lines for bottles or similar containers are known for adjusting the conveyor width, i.e., the spacing between railings on containers of different diameters (German Patent DE 43 30 702 A1, German Patent DE 697 09 943 T2, U.S. Pat. No. 6,382,882 B1). These railings are used to guide the containers laterally in a path and to prevent them from getting out of line across the direction of conveyance, which can lead to blockages in congested situations. In the known cases, adjustment of the railing is implemented by means of pneumatic cylinders, the end positions of which can define only two different positions. Furthermore, it is known that multiple pneumatic cylinders may be linked together to create more than two positions. The solution requires extensive assembly work, takes up a lot of space and causes a great complexity in terms of the control technology.